Roosting behaviors and roosting preference of flying foxes, Pteropus Vampyrus, were investigated in the Davao City Water District Malagos Watershed. As many as 2,604 flying foxes were counted roosting on two Terminalia copelandii (Lanipaw) trees. Behavioral units were identified then categorized in an ethogram as general maintenance behavior and social behavior. Activities of bats were sampled using the Instantaneous Sampling Method. Sleeping was the most dominant occurring behavior (80.42% on the roost. Sleeping positions by flying foxes were probably given by environmental conditions like weather, temperature and sunflecks. Other general maintenance behaviors were grooming (9.88%), locomotion (1.13%) searching (0.29%), stretching (0.33%), urinating (0.40%), defecating (0.43%), flying (2.64%), and fanning (2.25%). Social behaviors showed percent occurrences as: aggression (1.22%), courting (0.87%), and copulating (0.14%). Their roost site is 2 km from human habitation in Malagos. Two T. copelandii trees were found to be the primary roost trees. Endospermum peltatum (gubas) was also used by the flying foxes although less commonly. Both tree species have low canopy cover, and horizontal branching pattern and fissured barks. Flying foxes were not on served roosting on other big trees with high canopy cover and ascending branching patterns.